<!DOCTYPE html>
<html lang = "en" >
	<head >
		<meta charset = "UTF-8" >
		<title >Title</title >
		<style >
			details {
				border: 1px solid #aaa;
				user-select: none;
				padding: .5rem;
			}

			summary {
				font-weight: bold;
				margin: -0.5em -0.5em 0;
				padding: 0.5em;
			}
			details[open] summary {
				border-bottom: 1px solid #aaa;
			}
			details[open] summary::marker {
				color: #f00; /* 改变原生小箭头颜色 */
				/* content: ""; !* 去掉原生小箭头 *! */
			}
		</style >
	</head >
	<body >
		<details style = "width: 200px" >
			<summary >Details</summary >
			Something small enough to escape casual notice.
		</details >
		<span>123</span>
	</body >
</html >
